Thread: KFX Format
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Old 08-12-2015, 01:49 PM   #5
jhowell
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Posts: 1,785
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Join Date: Nov 2011
Location: Florida
Device: iPad Air 2, Kindle PW2, Nexus 7
I did some tests with my PW2 to experiment with the possibility of side-loading a book in kfx format. To do this I purchased and directly downloaded a free book to the kindle. I then switched into airplane mode and using USB I saved a copy of the book's main kfx file and the associated sdr directory. I deleted the book from the kindle and then made several attempts to side-load the book back to it, using a different file name each time.

I was able to successfully side-load. For this to work I needed the main kfx file, a directory of the same name with the suffix of '.sdr', and a subdirectory named 'assets' containing a small file named 'voucher' copied from the original download. This was sufficient to have the book show up as a personal document, but without a cover thumbnail, images, or a table of contents.

I then added the 'metadata.kfx' file that had originally been contained in the assets directory. That made the book functional again with a proper cover thumbnail, internal images and a working table of contents.

Finally I added an 'attachables' subdirectory within assets containing a file named 'CR!FYVV6BXDES0YQ4MCX4CG93WB1Z0B.kfx'. This didn't make any apparent difference in the working of the book in my quick test.

That last file contains a number of high quality jpeg-xr images from the book. I don't understand how the book worked without them. Perhaps there are lower quality images elsewhere as a fallback or perhaps there were cached images somewhere on the kindle.

I only have one kindle so I am unable to test whether this process would have allowed to book to be side-loaded to a different kindle. I suspect that it would not have worked due to DRM.

All of this gives me hope that if the kfx format is ever understood well enough, it may be possible to create and side-load non-Amazon books in kfx format and have them rendered with enhanced typesetting.
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